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BATCH MEMBERS :

BINITHA.B (10610103004)POOJA RAMDAS (10610103017)PREETHI.P (10610103019)RADHA.S (10610103305)

GUIDED BY :

Mrs. F. DEVAIRAKKAM RENU M.E.,Assistant Professor

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NON-DESTRUCTIVE TESTING (NDT):

Non destructive testing is a technique for checking

structural integrity after concrete hardening

without or partial damage to the concrete.

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OBJECTIVE:

To Study the use, methodology & applicability of

non destructive testing methods to monitor the

structural health.

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SCOPE:

Suggest the methodology to be followed &

applicability of non destructive testing.

Automatic interpretation of data from NDT, with the

goal of detecting flaws accurately and efficiently.

To propose retrofitting techniques for structures

failing in this kind of testing.

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Why NDT? Strength on concrete depends on material, proper mixing

& also workmanship at the time of placing

Conventional methods of testing of concrete does provide

solution to assess actual strength or internal structure after

hardening of concrete

In some cases, it required to assess of concrete damaged

due to fire or any other natural calamity due judge the

condition of structure

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Where to use NDT? Quality control of Construction , in situ

Confirming Workmanship

determining the position, quantity or condition ofreinforcement

Location of Cracks/Joints/Honeycombing

Confirming or locating suspected deterioration ofconcrete resulting from such factors as overloading,fatigue, external or internal chemical attack or change,fire, explosion, environmental effect.

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Various methods of NDT : Schmidt Rebound Hammer Test.

Ultrasonic Pulse Velocity- UPV Test.

Core Extraction for Compressive Strength Test.

Carbonation depth measurement Test.

Concrete Cover Measurement Test.

Half-cell potentiometer Test.

Chloride content Test.

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1) REBOUND HAMMER TEST

This test is performed by a Schmidt hammer,

also known as a Swiss hammer or a rebound

hammer.

It was invented by Ernst Schmidt, a Swiss

engineer in 1948.

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Rebound Hammer Test

StrengthSurface

Hardness

• Reference code: IS 13311 (Part 2) – 1992.

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Mechanism of Rebound Hammer

It Consist of a spring control hammer that slides on a plunger within a tubular housing. When the plunger is pressed against the surface of the concrete, the mass rebound from the plunger. It reacts against the force of spring. The Distance travelled by the mass, is called rebound number.

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Principle : The rebound of an elastic mass depends on the hardness of the surface against which mass strikes.

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The test is performed on a column of size 350mmx290mm to determine its hardness. The rebound numbers are obtained as below:

Point Rebound

number

Average rebound

number

1. 36

40

32

34

36

40

36.33

2. 42

42

36

38

38

42

39.66

3. 38

48

30

42

40

42

40

4. 44

36

46

36

40

40

40.33

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5. 40

44

44

46

44

42

43.33

6. 44

46

38

44

42

42

42.66

7. 42

36

44

44

32

36

39

8. 42

42

40

38

40

42

40.66

9. 30

32

34

30

32

30

31.33

10. 34

32

38

40

32

32

34.66

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11. 30

36

30

30

30

32

31.33

12. 32

34

32

32

44

30

34

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The test is performed on a cube of size 150mmx150mmx150mm to determine its hardness. The rebound numbers are obtained as below:

Cube

grade

M25

Point 1 2 3 4 5 6

Rebound

number

32

30

24

28

24

26

30

32

26

30

26

28

32

26

30

26

28

30

30

28

24

32

28

28

24

30

32

26

24

28

28

28

30

26

32

30

Average

rebound

number27.3

3

28.

66

28.6

6

28.33 27.33 29

Cube

grade

M40

Point 1 2 3 4 5 6

Rebound

number

38

40

44

36

40

38

42

40

44

38

36

38

44

36

42

38

40

42

40

38

42

36

44

40

44

38

40

36

38

40

42

36

38

44

40

40

Average

rebound

number39.

33

39.

66

40.3

3

40 39.33 40

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Average Rebound Number:

Average Rebound Number Quality of Concrete

>40 Very good hard layer

30 to 40 Good layer

20 to 30 Fair

< 20 Poor concrete

0 Delaminated

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Tested M40 cube

Good layer

Results:

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FACTORS AFFECTING THE TEST RESULTS:

Type of Cement

Type of Aggregate

Surface Condition and Moisture Content of Concrete

Curing and Age of Concrete

Carbonation of Concrete Surface

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2) ULTRASONIC PULSE VELOCITY-UPV TEST

This test is used for determination of the uniformity of

concrete in and between members and Detection of the

presence & approximate extent of cracks, voids & other

imperfection in concrete.

Reference code: IS 13311 Part I

Higher is the velocity, better is the quality of concrete

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The apparatus for ultrasonic pulse velocity measurement consists of the following:

(a) Electrical pulse generator(b) Transducer – one pair(c) Amplifier(d) Electronic timing device

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UPV methods

Direct method

Indirect method

Semi direct method

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Velocity criterion for concrete quality grading is given by

IS 13311 (Part-I):1992

Sl. No.Ultrasonic Pulse Velocity by Cross

probing (Km/Sec)Concrete quality grading

1 Above 4.5 Excellent

2 3.5 to 4.5 Good

3 3.0 to 3.5 Medium

4 Below 3.0 Doubtful

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DIRECT METHOD

Path

length

(m)

Point velocity (km/s)

A B

0.290

1 3.75 4.46

2 3.44 4.08

3 3.46 4.10

4 3.45 4.02

5 3.65 4.29

6 3.77 4.13

7 4.13 4.36

The test is performed on a column of size

350mmx290mm and the values are obtained as below:

INDIRECT METHOD

Path

length

(m)

Point velocity (km/s)

A

0.200

1 3.08

2 2.87

3 2.83

4 2.99

5 3.22

6 3.085

7 3.10

SEMIDIRECT METHOD

Path

length

(m)

Point velocity (km/s)

A

0.316

1 3.76

2 3.64

3 3.35

4 3.54

5 3.42

6 3.45

7 3.70

Good

Medium

Good

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Concrete

grade

velocity (km/s)

DIRECT METHOD SEMIDIRECT

METHOD

M25 4.348

4.286

4.644

4.206

4.240

3.926

4.889

M40 4.688

4.836

4.718

4.511

4.711

4.417

4.417

M50 4.868

4.839

4.958

4.936

4.609

4.818

4.992

The test is performed on a cube of size

150mmx150mmx150mm and the values are obtained as

below:

Good

Excellent

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3) CORE EXTRACTION FOR COMPRESSIVE STRENGTH TEST

Reference Standard codes:

IS 516

IS 1199

SP 24

Apparatus for Core Extraction of concrete:

Core drill.

Saw for trimming the ends of the core.

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29

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Results:

M40 GRADE

Mold Load (KN) Area (mm2) Stress (N/mm2)

CUBE 982.5 150x150 43.67

CORE 617.5 π/4 x 138² 41.29

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4) CARBONATION DEPTH MEASUREMENT TEST

Carbonation of concrete occurs when thecarbon dioxide, in the atmosphere in thepresence of moisture, reacts with hydratedcement minerals to produce carbonates.

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The core retained itspurple color after thesolution is poured.Thus, the core stillretains its alkalinecharacteristic and nocarbonation had occur.

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5) CONCRETE COVER MEASUREMENT TEST

Profoscope is specially for detecting the,

Depth of concrete cover,

Rebar location and

Its orientation.

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Application:Profoscope is used to evaluatereinforced concrete structures:•Locate in structures embeddedwith reinforcement.•Locate in structures embeddedwith cable ducts.•Locate rebars upto 160mm.

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6) HALF-CELL POTENTIOMETER TEST

Reference code: ASTM standard C876-91

To assest reinforcement corrosion.

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The test is performed on a beam of size 600mmx300mmx60mm in which one half is casted with salt water and other half is casted with normal water.

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Half-cell potential reading, vs. Cu/CuSO4 Corrosion activity

less negative than -0.200 V 90% probability of no corrosion

between -0.200 V and -0.350 V an increasing probability of corrosion

more negative than -0.350 V 90% probability of corrosion

Probability of corrosion according to half-cell readings :

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Rebars

Half-cell potential reading (V)

Salt water casting Normal water casting

1 - 0.302

-0.288

-0.314

-0.243

-0.241

-0.258

2 -0.529

-0.477

-0.401

-0.296

-0.311

-0.283

3 -0.625

-0.627

-0.631

-0.172

-0.170

-0.159

Both side Increasing probability of

corrosion

Corroded and

increasing probability of corrosion

Corroded and Non-corroded

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FACTORS AFFECTING TEST RESULTS:

o WETTNESS OF SURFACE

o CARBONATION

o ELECTRIC CURRENT

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7) CHLORIDE CONTENT TEST

Reference code: IS:14959 Part – III – 2001

To determine the chloride content from the

powdered sample which is collected from the

concrete by drilling method.

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Sl.

No.

Volume of

pipette

solution

Burette reading Concordant

valueInitial Final

1

.

80ml 0 ml 16.6 ml 16.6 ml

Chloride content = x (equivalent value of chlorine x 250ml)

x (3.545x250)

=3.59 kg/m3

= 0.149%

=0.149 x in kg/m3

Test results Interpretations

Below 0.6 kg/m3 No corrosion.

Above 0.6 kg/m3 High chloride attack.There is high chloride attack on the selected concrete.

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Conclusion : Various NDT methods can be used depending upon

the type & age of structure to check the integrity ofstructure.

USPV, rebound hammer & cover meter can be appliedto newly constructed structures to check the quality ofconcrete adequacy of cover before applying live load tothe structures.

Half cell potentiometer & carbonation test can beapplied to old structure to access to carbonation depth& amount of corrosion occurred.

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Remedial measures: Replacement of cover concrete by microconcrete

Polymer Modified Mortar Treatment

Protective Coating

Jacketing

Water proofing to slab

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